In a meeting, a video conference system or a general video conference software controls the data bandwidth of a image in order to keep a video image a certain quality. The data bandwidth is also a bit rate of a compressed video image. Currently, there are mainly two mechanisms to manage the data bandwidth: one is to set a video stream bit rate a default, the other one is to detect in real-time a current network bandwidth and determine the video stream bit rate according to the current network bandwidth. For the first mechanism, because the data volume of the compressed video image is determined by the complexity of a current video image, setting the video stream bit rate to default may obtain an unclear compressed transmission image or waste the network bandwidth. For the second mechanism, the current network bandwidth is dynamically detected, so the bit rate of the compressed video image will be continually increasing with the current network bandwidth becoming broader, which necessarily wastes the network bandwidth while a low bit rate may ensure the transmission video image is clear.